The linear motor mobile coil as described in Japanese Patent Application Laid-open No. 2002-112524 is cited as an example of prior art related to the present invention. The object of this mobile coil is to enhance the heat radiation effect of the linear motor mobile coil. This mobile coil is comprised of 4 multilayered substrates, wherein a plurality of coils made of spiral conductor patterns are formed in alignment on each layer. The coils of each layer are electrically connected to each other by means of through holes via an insulating layer.
In the above mobile coils, compared to conventional mobile coils in which wires were lap wound, the heat radiation effect can be enhanced by increasing the heat radiation area of the conductor pattern through which the electrical current flows. Also, since the allowable current density of the conductor pattern can be increased by enhancing the heat radiation effect, the amount of copper used for the mobile coil in order to obtain the desired motor output can be reduced. This enables a lighter mobile coil and improved motor efficiency.
However, the above-mentioned precedent technology results in the following problems. Firstly, since the coil comprising 4 multilayer substrates, wherein a plurality of coils made of spiral conductive patterns are formed in alignment on each layer and wherein the coils of each layer are electrically connected to each other by means of through holes via an insulating layer is a mobile coil, the coil drive circuit cannot be formed on the multilayered substrate. This results in a complex structure. Secondly, although the heat radiation effect can be enhanced by increasing the heat radiation area of the conductor pattern, this heat radiation effect remains insufficient.